Portable heater

ABSTRACT

A heater is provided with a heater core having a source of thermal energy in a heat exchange relationship with a heat exchanger. A fan moves air through the heater core from an air inlet to an air outlet. The heater core is thermally insulated by an air jacket from an exterior case.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/755,746filed Apr. 7, 2010, which claims the benefit of U.S. ProvisionalApplication No. 61/167,339, filed Apr. 7, 2009, the entire disclosure ofeach of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to a heater, and morespecifically, to a portable or space heater.

BACKGROUND OF THE INVENTION

With the diminishing supply of fossil fuels and their associatedspiraling costs, more homes and businesses are using space heaters astheir primary or secondary heating source. It is beneficial for suchspace heaters to be easy to service and thermally efficient.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a heater isprovided comprising an exterior case comprising an air inlet and an airoutlet and a heater core within the exterior case and being incommunication with the air inlet and the air outlet. A fan communicateswith the air inlet and the air outlet for moving air through the heatercore. The heater core comprises a source of thermal energy and a heatexchanger. The heat exchanger comprises an inner cylinder and an outercylinder. The inner cylinder is disposed adjacent and surrounding thesource of thermal energy and the outer cylinder surrounds the innercylinder to define an intermediate chamber between the inner and outercylinders. The inner and outer cylinders of the heat exchanger are eachoriented along a longitudinal axis extending between walls of theexterior case wherein the air inlet and air outlet are disposed.

In accordance with another aspect of the present invention, a heatercomprises an exterior case comprising an air inlet and an air outlet anda heater core within the exterior case and being in communication withthe air inlet and the air outlet. A fan communicates with the air inletand the air outlet for moving air through the heater core. The heatercore comprises a source of thermal energy and a heat exchanger. The heatexchanger is disposed within the heater core and extends along alongitudinal axis extending between walls of the exterior case whereinthe air inlet and air outlet are disposed. The heat exchanger comprisesan inner cylinder surrounding the source of thermal energy and an outercylinder surrounding the inner cylinder. An air pathway defines a pathof air movement progressing from the air inlet, through the heatexchanger, and out the air outlet, wherein the air pathway progressesthrough the heater in a direction substantially parallel to thelongitudinal axis.

In accordance with another aspect of the present invention, a heatercomprises an exterior case comprising an air inlet and an air outlet anda heater core within the exterior case and being in communication withthe air inlet and the air outlet. A dividing wall separates the heatercore into a first portion adjacent the air inlet and a second portionadjacent the air outlet. The dividing wall inhibits fluid communicationbetween the air inlet and air outlet, and the dividing wall furthercomprises an opening extending therethrough. A fan communicates with theair inlet and the air outlet for moving air through the heater core. Theheater core comprises a source of thermal energy and a heat exchanger.The heat exchanger is disposed within the heater core and comprises aninner cylinder surrounding the at least one source of thermal energy andan outer cylinder surrounding the inner cylinder. The heat exchanger isin fluid communication with the opening, such that air moving throughthe heater core from the first portion to the second portion is forcedto proceed through the heat exchanger prior to being discharged throughthe opening and thereafter through the air outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example heater.

FIG. 2 is a side, partial detail view of the heater of FIG. 1.

FIG. 3 is an exploded, perspective view of the heater of FIG. 1.

FIG. 4 is front perspective view of an example heat exchanger.

FIG. 5 is similar to FIG. 4, but shows a rear perspective view.

FIG. 6 is a perspective view of the heat exchanger of FIG. 4 coupled toan example heater core.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Turning to FIGS. 1 and 2, reference numeral 10 refers to an exampleportable heater, which may be referred to herein as a space heater.Heater 10 comprises an exterior case 12, a heater core support 14mounted inside exterior case 12 and a heater core 16 supported by heatercore support 14. The heater core 16 can include various structure forheating air passing therethrough, such as sources of energy, heatexchangers, etc. Where possible, the various structural elements can becoupled together by a minimal number of fasteners and joints, such as bya minimal number of screws or the like, projections received in slots,or other removable or even non-removable locking structure, for improvedserviceability. Further, the heater 10 can include various otherelements, such as described in U.S. Pat. Nos. 6,327,427 and 7,046,918,the contents of which are incorporated herein by reference in theirentirety.

Exterior case 12 can be a generally box-like structure including a frontwall 18, a rear wall 20, a top wall 22, a bottom wall 24 and side walls26, 28. An air inlet 30 is provided in rear wall 20 and an air outlet 32is provided in front wall 18. As will be described herein, air can flowthrough the heater 10 generally along the direction of arrow F. Airinlet 30 and air outlet 32 can be covered with protective grilles,respectively. In addition or alternatively, a filter 42 can bepositioned over air inlet 30 and/or air outlet 32. For example, thefilter 42 may be attached to rear wall 20 with various fasteners, suchas hook-and-loop style fasteners or the like. Filter 42 may be ofconventional construction, for example fiberglass or equivalent materialas is commonly used in furnace filters. In one example, the filter 42can be a POLYTRON filter or similar. Some or all of the walls, such asany of the front wall 18, top wall 22 and bottom 24 wall may beintegrally formed as a wrapper to which side walls 26, 28 are formedwith or joined with sheet metal screws, rivets, and/or by otherconventional methods of construction such as welding, brazing and theuse of fasteners, such a projection received in a slot, or combinationsof methods as is known in the art. In one example, the top wall 22 andboth side walls 26, 28 can be formed from a single sheet of material,which can be bent to define the top wall 22 and side walls 26, 28. Inaddition or alternatively, the heater 10 can be supported by one or morestationary or movable feet coupled to the bottom wall 24. In oneexample, the feet can be rotatable wheels 118, such as casters. Thebottom wall 24 can include recesses, through holes, or the like to allowthe casters to be at least partially recessed into the bottom wall 24such that the heater 10 can be positioned relatively closer to a flooror other supporting surface. In one example, the rotatable wheels 118can be coupled to the bottom wall 24 by mechanical fasteners, adhesives,welding, or even by a twist-lock arrangement, which can be similar to ordifferent than the heat exchanger 90 mounting described herein.

Exterior case 12 generally encloses heater core support 14. Heater coresupport 14 can comprise a front mounting panel 52 and a rear mountingpanel 54. In addition or alternatively, front mounting panel 52 may bespaced a distance from front wall 18, or may be directly adjacentthereto. For example, the front wall 18 can include a decorative plasticpanel coupled to the mounting panel 52. The front mounting panel 52 canbe secured to at least one of the top wall 22, bottom wall 24 and sidewalls 26, 28. In one example, front mounting panel 52 can be formedtogether with the bottom wall 24 (or even the top wall 22), such asbeing made out of the same sheet of metal, and may be bent relative tothe bottom wall 24 so as to be generally perpendicular to the bottomwall 24 to facilitate manufacturing. Alternatively, front mounting panel52 can be the same as the front wall 18. An aperture 58 is provided infront mounting panel 52 above which can be mounted a deflector shield 60for directing air towards air outlet 32. The deflector shield can bevisible from the exterior of the unit, and can be colored or otherwiseconfigured to be visually appealing.

The rear mounting panel 54 can be secured to at least one of top wall22, bottom wall 24 and side walls 26, 28 and can be spaced a distancefrom rear wall 20. In one example, the rear mounting panel 54 can becoupled to the bottom wall 24 by a mechanical fastener, such as a screw,rivet, or the like, and/or can also utilize a projection received in aslot for improved structural rigidity. In addition or alternatively, therear mounting panel 54 can include at least one, such as a pair, of areinforcing braces 25 coupled to the bottom wall 24. In another example,rear mounting panel 54 can be formed together with the bottom wall 24(or even the top wall 22), such as being made out of the same sheet ofmetal, and may be bent relative to the bottom wall 24 so as to begenerally perpendicular to the bottom wall 24 to facilitatemanufacturing. In one example, all of the bottom wall 24, front mountingpanel 52, and rear mounting panel 54 can be formed from a single sheetof metal.

The space between rear mounting panel 54 and rear wall 20 of exteriorcase 12 can form an intake chamber 62. In addition or alternatively, anintake manifold 63, in communication with a fan 66, can be providedwithin the intake chamber 62. The intake manifold 63 can be removably ornon-removably coupled to the rear mounting panel 54 in various manners,such as with sheet metal screws and/or by other conventional methods ofconstruction such as welding, brazing and/or the use of fasteners, sucha projection received in a slot, or combinations of methods as is knownin the art. In one example, the intake manifold 63 can hang onto therear mounting panel 54 by one or more projection-in-slot fasteners, andcan also be coupled to the rear mounting panel 54 by screws. The intakemanifold 63 can include at least one aperture 64 extending therethroughfor providing fluid communication between the fan 66 and the heater core16. For example, the fan 66 can be mounted to the intake manifold 63about the aperture 64 for drawing air into heater 10 though air inlet 30in rear wall 20 and forcing air out through the heater core 16 (viaaperture 58) and out the air outlet 32. Alternatively, the fan may belocated proximate the air inlet 30, to draw air in through that openingand direct it through the intake chamber 62 and aperture 64, and intothe heater core 16. Various fans operated at various speeds can be used,including axial, centrifugal, cross-flow, etc.

A conventional power cord 46 can extend from rear wall 20 for connectingthe electrical components within exterior case 12 to a conventional 110volt A.C. line. If desired, heater 10 may have a power cord strainrelief or the like installed in the hole through which power cord 46passes. In addition or alternatively, a variable thermostatic control 50can be mounted to either or both of the front wall 18 (shown) or even tothe rear wall 20 (not shown). The variable thermostatic control 50 caninclude analog and/or digital structure for adjusting a desiredtemperature or operational range (i.e., relatively hotter or cooler)and/or fan speed (i.e., relatively faster or slower), and may includevarious knobs, buttons, or other selector structure. In addition oralternatively, the thermostatic control 50 can include variouscircuitry, sensors, such as various temperature sensors, humiditysensor(s), etc., and/or timer(s). Similarly, the variable thermostaticcontrol 50 can include indicia or other indicator structure to provide avisual and/or audible display of the desired settings/selections.Input/output structure, which may be located at a convenient location(e.g., on the front or sides) may be electrically coupled but physicallylocated apart from control structure (e.g., circuitry, sensors, etc.)that may be located within the unit. Structure can be provided for avisual and/or audible display of service information, such as warnings,filter change notifications, energy source 78 change notifications, etc.Thermostatic control 50 communicates with the operative components ofthe heater 10, such as the thermal energy source(s) and/or fan(s), tocontrol operation thereof. An on-off switch (not shown) may be providedon front wall 18 or rear wall 20, if desired. An automatic-mode ormanual-mode switch (not shown) may also be provided on front wall 18 orrear wall 20, if desired. A switch (not shown) may also be provided tooperate the fan without the heating elements, so as to provide only aircirculation.

In an embodiment of heater 10, one or more (such as a pair) oftemperature sensors, which may also function as limit switches, can beprovided about the heater core 16. A first temperature switch 67 can belocated on or in heater core 16 to sense the air temperature inside theheater core 16. In one example, the first temperature switch is disposedclose to the rear mounting panel 54 (or even the front mounting panel52) adjacent where air enters (or exits) heater core 16, and acts as afan control switch. In one example, the first temperature switch 67 canbe mounted on a circuit board 65 or the like. When the temperature inheater core 16 rises above a predetermined temperature detected by thefirst temperature switch 67, such as 110 degrees F., fan 66 is switchedon. Delayed starting of fan 66 until after the thermal energy sourcesare energized can be preferred such that cold air is not forced throughair outlet 32. The first temperature switch 67 can act in reverse at theend of a heating cycle when heater 10 is shut off. In this mode, fan 66continues to operate until the temperature drops below a predeterminedtemperature, such as 110 degrees F., improving the efficiency of heater10 by extracting residual heat. A second temperature switch 69 can belocated to sense the air temperature inside the heater core 16 at adifferent location than the first switch 67 and can function as a safetyswitch. The second temperature switch 69 can be located towards the topof the heater core 16 and can be retained by a bracket 71. When thetemperature in heater core 16 rises above a predetermined temperaturedetected by the second temperature switch 69, such as 225 degrees F.,the thermal energy sources can be shut down as a safety feature whilesaid first temperature switch 67 keeps fan 66 running until thetemperature in heater core 16 falls below a predetermined temperature,such as 110 degrees F. It will be apparent that the temperatures atwhich the temperature switches 67, 69 operate are arbitrary and a mannerof design choice. Other switches may be used that are triggered atdifferent temperature levels, times, etc.

Heater core 16 can be supported (e.g., by the front mounting panel 52and the rear mounting panel 54) at a distance below top wall 22 andabove bottom wall 24 of exterior case 12 and a distance from side walls26, 28. This spacing of heater core 16 from exterior case 12 provides anair jacket 57 that extends at least partially about the heater core 16.In one example, the air jacket 57 can surround the heater core 16. Airjacket 57 can insulate the exterior case 12 to inhibit, such as prevent,overheating. In addition or alternatively, some or all of the interiorsurface(s) of the case 12 can include an insulating material. Forexample, the interior surfaces of the top wall 22 and side walls 26, 28can all include insulating material. In addition or alternatively, theintake chamber and/or intake manifold 63 may form a portion of the airjacket 57, and/or can provide similarly insulating functionality. Assuch, it is possible for heater 10 to be safely operated with theexterior case 12 remaining generally cool to the touch, and/or withexterior case 12 fitted into a wood cabinet or the like. In one example,the air jacket 57 can be in fluid communication with the air inlet 30via at least one opening 106 in the rear panel 54, and the air outlet 32via at least one opening 108 in the front panel 52, to provide a coolingairflow through the air jacket 57. The intake manifold 63 can bearranged in covering and fluid communication with the opening(s) 106such that positive airflow from the fan 66 is caused to flow into andthrough the air jacket 57 during operation of the heater 10. The airflowexiting the air jacket 57 via opening(s) 108 can proceed through atleast one aperture 109. In one example, the aperture 109 can be a gap,such as a ⅛″ clearance (or other dimension), located at the interfacebetween the front wall 18 and the front mounting panel 52 and in flowcommunication with the air outlet 32. The aperture 109 can be formed(e.g., molded or otherwise manufactured) into either or both of thefront wall 18 and front mounting panel 52. Thus, airflow exiting theopening(s) 108 can proceed through the aperture 109 to allow the airfrom the air jacket 57 to join and mix with the heated air exiting theheater core 16 through air outlet 32.

Heater core 16 generally comprises a top wall 70, a bottom wall 72 andside walls 74, 76 and is mounted upon front mounting panel 52 and rearmounting panel 54, which can define the end walls of the heater core.The heater core 16 can be mounted to the front and/or rear panels 52, 54in various manners, including sheet metal screws, rivets, and/or byother conventional methods of construction such as welding, brazing andthe use of fasteners, such a projection received in a slot, orcombinations of methods as is known in the art. For example, the heatercore 16 can be removably or non-removably coupled to the front and rearmounting panels 52, 54 in various manners, including fasteners, welding,adhesives, etc. In addition or alternatively, portions of the heatercore 16 and/or front and rear mounting panels 52, 54 can includematching projections-in-slots to facilitate coupling thereof.

The heater core 16 can have various geometries to guide the airflowtherethrough. For example, as shown, a first portion 73 of the heatercore 16 located relatively closer to the rear wall 20 can have sidewalls 74, 76 of a generally uniform vertical dimension extending betweenthe top 22 and bottom 24 walls, while a second portion 75 of the heatercore 16 located relatively closer to the front wall 18 can have sidewalls 74, 76 with a changing vertical dimension extending in a directionbetween the top 22 and bottom 24 walls. For example, as shown, thesecond portion 75 can have a generally tapered geometry that graduallyreduces the cross-sectional flow area defined by the side walls 74, 76as the side walls 74, 76 approach the front wall 18 to thereby directthe air flow towards the outlet 32, and/or increase the exit velocitythereof by reducing the cross-sectional flow area. In addition oralternatively, the side walls 74, 76 of the first and second portions73, 75 can have a generally uniform horizontal dimension extending in adirection between the side walls 26, 28 of the exterior case 12, or evenhave a changing horizontal dimension extending in a direction betweenthe side walls 26, 28 of the exterior case 12 that tapers inwards.

Additionally, the heater core 16 can include a dividing wall 81 disposedbetween the first and second portions 73, 75. As will be furtherdescribed, the dividing wall 81 can inhibit, such as prevent, fluidcommunication between the first and second portions 73, 75. The dividingwall 81 can include various sealing structures to facilitate dividingthe first and second portions 73, 75.

The heater core 16 includes at least one thermal energy source 78, suchas an infrared emitter, mounted between side walls 74, 76. In heater 10shown in the drawings, mountings for three thermal energy sources 78 areprovided with the sources 78 being mounted horizontally in a directionthat extends generally between the front and rear walls 18, 20. Inaddition or alternatively, horizontal mounting of energy sources 78 ispreferred as this arrangement improves serviceability of the heater 10as will be further described.

Various example energy sources 78, such as radiant energy sources, canbe utilized. For example, each thermal energy source 78 can comprise ahigh resistance wire wrapped in a helical configuration. The helicallyconfigured element is suspended within a quartz tube. The tube is cappedwith ceramic end pieces or caps 80. The tube may be vacuum sealed andmay contain an inert gas. The quartz tube may be clear, semi-translucentor translucent. In a preferred embodiment, the thermal energy source 78is linear and has a clear quartz tube. In one example embodiment, eachof three energy sources 78 is 500 watts, where each source 78 drawsabout 4 amps. Thus, the total energy usage for operating the heater 10is about 1500 watts so as to be operable on a standard household 110VA.C. outlet. Still, the thermal energy source 78 can have variousgeometries, such as curved, polygonal, random, etc.

As shown in FIGS. 3-5, each energy source 78 can be provided within aheat exchanger. For example, a heat exchanger 90 is preferably in theform of a sheet of metal, such as copper or aluminum that may or may notbe pretreated, and fashioned into a cylindrical geometry mounted aroundeach of thermal energy source 78. Each heat exchanger 90 can be receivedin a hole 82 in the rear mounting panel 54, and can be configuredvariously, such as a tube-in-tube arrangement, as will be described. Inone example, the heat exchanger 90 can include an inner cylinder 94 andan outer cylinder 96. The inner cylinder 94 can be arranged adjacent to,such as to face and/or surround, the associated thermal energy source78, and the outer cylinder 96 can be arranged adjacent to, such as toface and/or surround, the inner cylinder 94. The inner cylinder 94 canhave a relatively smaller cross-sectional area compared to the outercylinder 96 so as to define an intermediate chamber 100 defined in theannular space therebetween. For example, the inner and outer cylinders94, 96 can have a generally circular cross-sectional geometry, and thediameter of the inner cylinder 94 can be relatively smaller than thediameter of the outer cylinder 96. The inner cylinder 94 can have twogenerally open ends, such that air can flow therethrough, while theouter cylinder 96 can include at least one closed end 104, such that airflowing within the outer cylinder 96 is redirected. For example, asshown in FIG. 2, such an arrangement of the heat exchanger 90 can createa serpentine, circuitous “S”-shaped path for the airflow when viewed incross-section.

In addition or alternatively, the inner cylinder 94 can be arrangedgenerally concentric with the outer cylinder 96, though other relativearrangements are also contemplated. In addition or alternatively, theouter cylinder 96 may extend only partially along the length of theinner cylinder 94, so as to create a gap 99 therebetween. In addition oralternatively, the inner and outer cylinders 94, 96 can be coupledtogether in various manners, such as with sheet metal screws and/or byother conventional methods of construction such as welding, brazing andthe use of fasteners, such a projection received in a slot, orcombinations of methods as known in the art. In addition oralternatively, each heat exchanger 90 can include a mounting plate 93coupled to the closed end 104, and spaced a distance from the closed end104 to define one or more air passages 116. Thus, when the mountingplate 93 is coupled to the rear mounting panel 54, air passing throughholes 82 in the rear mounting panel 54 can flow around the heatexchanger 90, via the air passages 116, and into the first potion 73 ofthe heater core 16. In addition or alternatively, air from the fan 66can also pass into the first portion 73 of the heater core 16 throughother holes 107 in the rear mounting panel 54. For example, the intakemanifold 63 can be arranged in a covering relationship and in fluidcommunication with each of the holes 82 and holes 107, such thatpositive airflow from the fan 66 is caused to flow into the firstportion 73 of the heater core 16 via all of the passages 116 and holes107.

Each energy source 78 can be retained within a respective heat exchanger90 by a bracket 97 or the like. In addition or alternatively, the otherend of the energy source 78 can be retained by having a cap 80 thereofcoupled to supporting structure 112, or even to one end of the outercylinder 96. Either or both of the caps 80 can be adapted to retain thethermal energy source 78 mounted through hole 82 in various manners,such as via a snap-lock arrangement or the like. Thus, each cap 80 andsource 78 can be designed to have a unique socket structure tofacilitate replacement of a source 78 by a repair technician or even bythe end-user. Electrically conductive wires can pass through the hole82, or may be provided to either of the end caps 80, for energizingenergy source 78. The electrically conductive wires can be pig-tailed atone end only, such as at the end adjacent the first portion 73 of theheater core 16 (i.e., more towards the rear wall 20) to furtherfacilitate the replacement of a source 78 by a repair technician or evenby the end-user. For example, as shown in FIG. 4, one of the end caps 80can have an electrical plug 89 adapted to fit into electrical socketstructure to facilitate de-coupling each source 78 for replacement.

The bracket 97 can provide easy and quick serviceability of the energysource 78. In one example, the bracket 97 can be coupled to the heatexchanger 90 by having one end 120 fit into a slot of the mounting plate93 while the other end 122 receives a mechanical fastener or the like.As shown in FIG. 4, the bracket 97 can also include a retaining plate124 adapted to positively couple the energy source 78 to the heatexchanger 90. For assembly, the energy source 78 can be inserted into ahole in the closed end 104 of the heat exchanger 90. The one end 120 ofthe bracket 97 can be fit into the slot of the mounting plate 93. In oneexample, the one end 120 can have a bent or curved profile to permit thebracket 97 to be coupled to the mounting plate 93 in a pivoting,cantilever fashion. The bracket 97 can be pressed down until theretaining plate 124 presses upon the cap 80 of the energy source 78 suchthat the cap 80 is retained between the closed end 104 and the retainingplate 124. A portion of the end cap 80 with the electrical plug 89 canextend through a hole in the retaining plate 124 to be coupled to theelectrical socket structure. The bracket 97 can then be retained inplace by removably coupling the other end 122 to the mounting plate 93by a mechanical fastener (e.g., screw, bolt, nut, etc.) or the like. Inone example, a single mechanical fastener can be used. Disassembly canbe performed in reverse. During disassembly, the bracket 97 can be atleast partially removable from the heat exchanger 90 to permitreplacement of the energy source 78. Upon loosening or removal of thefastener, the end 122 can be separated from the heat exchanger 90. Inother examples, the end 120 of the bracket 97 can remain pivotallycoupled to the mounting plate 93, or can be completely removedtherefrom. With such structure, individual energy sources 78 can bequickly and easily replaced with little disassembly and few fasteners,such as by only removing the intake manifold 63 and one bracket 97,while the associated heat exchanger 90 need not be removed.

Mounting tabs 92 are provided on one end of heat exchanger 90 forattachment of said heat exchanger 90 in one of the corresponding holes82 provided in rear mounting panel 54. Three generally similar holes 82are provided in the rear panel 54 to each receive a separate one of thethree heat exchangers 90, though various numbers of heat exchangers arecontemplated. Each hole 82 can include one or more recesses 88corresponding generally to the number of mounting tabs 92 provided toeach heat exchanger 90. In the shown example, each heat exchanger 90 hasthree generally evenly spaced mounting tabs 92 and each hole 82 hasthree corresponding recesses 88. Each mounting tab 92 can be offset adistance from the mounting plate 93 of the heat exchanger 90. Eachmounting tab 92 can have one end coupled to the mounting plate 93, andhave the other end be free or detached from the mounting plate 93.

In one example, to couple a heat exchanger 90 to the rear panel 54, theheat exchanger 90 is inserted into the hole 82 with each mounting tab 92being inserted into an associated recess 88. Next, the heat exchanger 90can be rotated along the direction of arrow T, in a twist-lockarrangement, such that a portion of the rear panel 54 is captured in theoffset space between each mounting tab 92 (i.e., via the free end) andthe mounting plate 93. The bracket 97 can be utilized as a handle tofacilitate the twisting. In addition or alternatively, each heatexchanger 90 can include various structure for positive retention withinthe rear panel 54. In one example, the mounting plate 93 of each heatexchanger 90 can include one or more holes 95 for further coupling theheat exchanger 90 to the rear panel 54 by a mechanical fastener (i.e.,screw, rivet, or other fastener). In another example, mounting plate 93can include an anti-rotation stop 114, such as a projection or the like,to inhibit rotation for removal of the heat exchanger 90 unless the stop114 is depressed. Thus, the energy source 78 can be coupled to the heatexchanger 90 (i.e., via the bracket 97) such that the heat exchanger 90can be removed as a modular unit from the heater 10 to facilitate easyreplacement of the energy source 78, as well as easy manufacturing.

The length of the heat exchanger 90 can be generally shorter than thespacing between the front and rear mounting panels 52, 54 of heater core16 so that there is a gap between a free end of heat exchanger 90 andthe front mounting panel 52. In one example, the length of the heatexchanger 90 is generally at least as long as the length of the firstportion 73 such that the heat exchanger 90 extends at least partiallyinto the second portion 75 through the dividing wall 81. In one example,the inner cylinder 94 can extend at least partially into the secondportion 75 through the dividing wall 81. In addition or alternatively,divider panels (not shown) can be provided for partitioning the insideof heater core 16 such that each heat exchanger 90 is in a separatecompartment.

In addition or alternatively, the heat exchanger can further include aspacing coupler 102 extending between and coupling the inner cylinder 94to the outer cylinder 96. For example, as shown in FIGS. 2-3, thespacing coupler 102 can be disposed generally within the outer cylinder96 in a close-fitting arrangement, such as a frictional or interferencefit. Another portion of the spacing coupler 102 can be coupled to an endof the relatively smaller diameter inner cylinder 94 to thereby providea supporting structure extending between and coupling the inner cylinder94 to the outer cylinder 96. In addition or alternatively, an openportion of the spacing coupler 102 can provide additional support forthe energy source 78. In addition or alternatively, the spacing coupler102 can be adapted to direct the airflow through the heat exchanger 90,such as to impart a swirling motion to the air passing through the heatexchanger 90. For example, as shown, the spacing coupler 102 can includea plurality of fins to direct the airflow. Some or all of the fins canalso be coupled to an end of the relatively smaller diameter innercylinder 94.

When heat exchanger 90 is formed of copper material, the copper can bepretreated at temperature and for a time sufficient to soften the coppermaterial and to partially blacken the surface of the copper material. Inan example embodiment, heat exchanger 90 can be formed from sheet copperhaving a thickness of 0.0216 inch and an oxygen content of 0.028% byweight. Heat exchanger 90 can be heated in an oven under ambientconditions for several hours at a temperature from about 850 degrees F.to about 900 degrees F. Any loose blackened material is removed by drybrushing inner cylinder 94 and outer cylinder 96 of heat exchanger 90.Good results have been obtained when heat exchanger 90 is heated for twohours at a temperature between about 850 degrees F. and 875 degrees F.,after which heat exchanger 90 is dry brushed and then further heated forone hour at 425 degrees F. It is believed that equally good resultswould be obtained when heat exchanger 90 is heated for three hours at875 degrees F. and then dry brushed to remove any loose particles.Removal of loose particles prevents them from being swept out air outlet32 when heater 10 is first operated. Pretreatment of the copper canimprove the heat efficiency of heater 10 by increasing the absorptivityand emissivity of heat exchanger 90 and roughening the walls of theinner and/or outer cylinders 94, 96 for more turbulent air flow.Optionally, the aforementioned copper composition and heat treatment maybe applied to only the inner cylinder 94. Still, some or all of thecopper material may not be pretreated.

When heat exchanger 90 is formed of aluminum material, the aluminum canbe pretreated by anodizing. During the anodizing process, a clear filmof aluminum oxide is laid down on the aluminum's surface. For use inheater 10, inner cylinder 94 of heat exchanger 90 is electrolyticallycolored a dark color to improve the material's radiant-heat properties,i.e., absorptivity and emissivity. It will be understood that outercylinder 96 may also be electrolytically colored. Still, either or bothof the cylinders 94, 96 (or even additional elements) can be formed fromvarious other materials, such as various metals (e.g., steel), ceramics,etc. that may or may not be pretreated.

The dividing wall 81 in the heater core 16 can include at least oneopening extending therethrough, such as a plurality of holes 83extending therethrough. Each of the holes 83 can cooperate with, such asreceive, a portion of a heat exchanger 90 so as to thereby enable fluidcommunication between the first and second portions 73, 75, via the heatexchanger(s) 90. In one example, as shown in FIG. 6, the heat exchanger90 can be coupled to the dividing wall 81 about the hole 83, such thatair moving through the heater core 16 is forced to proceed through theheat exchanger 90 prior to being discharged through the air outlet 32.For example, a portion, such as an end, of the inner cylinder 94 can becoupled to the dividing wall 81 about the hole 83 and can extend atleast partially through the dividing wall 81 via the hole 83. The innercylinder 94 can be removably or non-removably coupled to the dividingwall 81 in various manners, including fasteners, adhesives, welding,etc. and/or in a close-fitting arrangement, such as a frictional orinterference fit, etc.

In one example, as shown in FIG. 2, the dividing wall 81 can force airmoving through the heater core 16 to proceed through the heatexchanger(s) 90. Heater core 16 forms a plenum from which air is forcedthrough heat exchangers 90 passing over energy sources 78 in the innercylinders 94 of heat exchangers 90. For example, cool air is first drawninto the first portion 73, is heated by passage through the heatexchangers 90, and is exhausted through the second portion 75 and out ofthe air outlet 32. The first portion 73 can be a common input plenumfeeding input air into each of the heat exchangers 90, while the secondportion 75 can be an independent common output plenum receiving outputair from each of the heat exchangers 90. In one example, the heater core16 can include three heat exchangers 90, each including at least onethermal energy source 78 (e.g., about 500 watts each) as previouslydescribed herein. As shown in FIG. 6, each of the holes 83 in thedividing wall 81 can correspond generally with each of the holes 82 ofthe rear panel 54 such that each heat exchanger 90 can be orientedgenerally horizontally in a direction extending between the front andrear faces 18, 20 of the housing. For example, a portion of the innercylinder 94 can be received within a corresponding hole 83, and can beremovably or non-removably coupled thereto. In addition oralternatively, the inner cylinder 94 can include retaining structure 91(see FIG. 5), such as an annular ring or the like, that can be adaptedto retain the inner cylinder 94 within the hole 83.

In addition or alternatively, an auxiliary thermal energy source, suchas an infrared emitter (not shown), may be mounted adjacent front wall18 of exterior case 12 and front mounting panel 52 below air outlet 32.The auxiliary energy source can boost the temperature of the air passingout of heater 10 through air outlet 32. In addition, radiation from theauxiliary energy source can be reflected by copper deflector shield 60to provide a comforting warm glow seen through grille 34 over air outlet32. It should be understood that deflector shield 60 may also be formedof pretreated copper or aluminum but the glow through grille 34 may besomewhat compromised. In one embodiment of heater 10, auxiliary energysource can be a 250 watt quartz heating tube or other wattage.

Thus, as shown in FIG. 2, the instant design can form an air pathwaydefining a path of air movement progressing through the heater 10. Forexample, the air pathway can include some or all of the following toprogress from the air inlet 30, to the intake chamber 62 and through theholes 82 via air passage 116 (or other holes) into the first portion 73of the heater core 16, along the length of the outer cylinder 96 of theheat exchanger 90, through the intermediate chamber 100, through theinner cylinder 94, along the length of the thermal energy source 78,into the second portion 75 of the heater core 16, and out the air outlet32.

In one example operation, thermostatic control 50 switches on energysources 78 (and auxiliary heater, if present) whenever the temperaturewithin the environment monitored by the thermostat drops below apredetermined minimum. Power is also supplied to fan 66 causing the fanto be activated. When temperature switch 67 is provided, activation offan 66 may be delayed until the temperature in heater core 16 has risento a selected temperature. This is done so that the air coming fromheater 10 is warm on startup.

Upon being energized, energy sources 78 emit heat rays which areabsorbed and reemitted by heat exchangers 90. Activation of fan 66causes air to be circulated through heater 10. The circulating air isinitially forced into intake chamber 62 through air inlet 30. As shownin FIG. 2, the air provided by fan 66 passes through the holes 82 of therear panel 54, around the heat exchangers 90, and into the first portion73 of the heater core 16. Though not shown, it is to be understood thatthe fan 66 can be mounted directly over the aperture(s) 82, such thatthe output of the fan 66 can flow directly into the aperture(s) 82. Thedividing wall 81 inhibits, such as prevents, the air from enteringsecond portion 75 and forces the air to enter each heat exchanger 90through the gap 99 between the inner and outer cylinders 94, 96 suchthat the air is directed to take a serpentine, circuitous “S”-shapedpath (when viewed in cross-section) though the intermediate chamber 100defined between the outer cylinder 96 and the inner cylinder 94.

As the air passes through intermediate chambers 100, the air is heatedby radiant energy from energy sources 78 and also by energy reemitted byportions of the heat exchangers 90 (e.g., cylinders 94, 96) before itenters the inner-most portion of the heat exchanger to flow directlypast the energy source 78. The heated air then exits the heat exchanger90 and flows directly into the second portion 75 of the heater core 16,and is then directed out of the outlet 32. The inner and outer cylinders94, 96 of said heat exchanger 90 can each be oriented along alongitudinal axis substantially aligned along a direction from the airinlet 30 to the air outlet 32. For example, the longitudinal axis canextend in a horizontal direction aligned perpendicular and between therear wall 20 having the air inlet 30 and the front wall 18 having theair outlet 32. The longitudinal axis can extend along the direction ofarrow F.

Despite the serpentine pathway, the airflow pathway through the heater10 is predominantly generally parallel to an axis perpendicular to andextending between the walls where inlet 30 and outlet 32 are located,such that a pressure drop is reduced, such as minimized, between theinlet 30 and outlet 32, which can thereby further increase theefficiency of the heater 10. For example, conventional heaters mayutilize three or more directional changes of the airflow, each of whichcauses an associated pressure drop. In the instant application, thenumber of directional changes of the airflow is reduced to two in theserpentine path through the heat exchanger 90. Indeed, the flowdirection of the air pathway (i.e., along the direction of arrow F) caninclude the serpentine pathway progressing through the heat exchanger90. In one example, the air pathway can progress through the heater 10substantially parallel to the longitudinal axis (i.e., in the directionof arrow F) and the heat exchanger(s) 90. In addition or alternatively,the thermal energy source 78 can be mounted within the heater core 16along an axis generally parallel to said longitudinal axis (i.e., alsoalong the direction of arrow F).

For example, orienting the heat exchangers 90 to be generally parallelto the direction F between the inlet 30 and outlet 32 can reduce thenumber of U-turns performed by the heated air to only two turns (i.e.,via the serpentine “S”-shaped pathway). As a result, the heater 10described above can be relatively more efficient than a conventionalheater. Moreover, the heater 10 can further increase the overallefficiency by putting more heat into the air, keeping the exterior case12 and cabinet relatively cooler. In addition or alternatively, aportion of the airflow from the fan 66 can proceed through theopening(s) 106 and directly into the air jacket 57 to further keep theexterior case 12 and cabinet relatively cooler. In addition oralternatively, the heater 10 described above can further increase theoverall efficiency by positioning the energy sources 78 very close tothe outlet 32, such that air heated by the energy sources 78 flowsdirectly through the second portion 75 and out of the outlet 32, withlittle if any intermediate structure therebetween.

A single heater 10 as described can effectively heat up to 800 squarefeet, or even more, and is capable of safely increasing the temperatureof the air drawn through the unit by approximately 120 degrees F. It isbelieved the thermal efficiency of heater 10 is affected by pretreatmentof copper heat exchangers 90. In the embodiments described above, it isbelieved the heater 10 is more thermally efficient than a space heaterwherein the copper cylinders have not been pretreated. It is furtherbelieved that this improvement results more heat from the same amount ofpower used. Other efficiencies may result from stripping residual heatfrom heater core 16 on shut down with high temperature limit switch andfrom the pathway of the air through heat exchangers 90 which canincrease the dwell time of the air in heater core 16. It will beapparent that other design features discussed above also contribute tothe space heater's thermal efficiency.

The invention has been described with reference to the exampleembodiments described above. Modifications and alterations will occur toothers upon a reading and understanding of this specification. Examplesembodiments incorporating one or more aspects of the invention areintended to include all such modifications and alterations insofar asthey come within the scope of the appended claims.

What is claimed is:
 1. A heater, comprising: an exterior case comprisingan air inlet and an air outlet; a heater core within the exterior caseand being in communication with the air inlet and the air outlet; a fancommunicating with the air inlet and the air outlet for moving airthrough the heater core; said heater core comprising a source of thermalenergy and a heat exchanger, the heat exchanger comprising an inner ductand an outer duct, the inner duct being disposed adjacent andsurrounding the source of thermal energy and the outer duct surroundingthe inner duct to define an intermediate chamber between the inner andouter ducts; said inner and outer ducts of said heat exchanger eachoriented such that they extend along a direction between walls of saidexterior case wherein said air inlet and air outlet are disposed, andwherein the heat exchanger is removably coupled to the heater to permitremoval of a modular unit comprising the outer duct and the source ofthermal energy.
 2. The heater of claim 1, wherein the inner duct isarranged generally concentric with the outer duct.
 3. The heater ofclaim 1, further comprising a dividing wall separating the heater coreinto a first portion adjacent the air inlet and a second portionadjacent the air outlet, the dividing wall inhibiting fluidcommunication between the air inlet and air outlet.
 4. The heater ofclaim 3, wherein the dividing wall has an opening extending therethroughand the heat exchanger is in fluid communication with the opening, suchthat air moving through the heater core from the first portion to thesecond portion is forced to proceed through the heat exchanger.
 5. Theheater of claim 1, further comprising an air jacket extending at leastpartially between the exterior case and the heater core, the air jacketbeing adapted to provide a cooling airflow through the air jacket thatdoes not pass through the heater core.
 6. The heater of claim 5, saidair jacket being in fluid communication with the air inlet and the airoutlet in said exterior case.
 7. The heater of claim 1, wherein the heatexchanger comprises a bracket adapted to positively couple the source ofthermal energy to the heat exchanger, the bracket being at leastpartially removable from the heat exchanger to permit replacement of thesource of thermal energy without removal of the heat exchanger from theheater.
 8. The heater of claim 1, wherein the source of thermal energyis concentric with said inner and outer ducts such that they all share acommon longitudinal axis.
 9. The heater of claim 1, wherein the heatexchanger comprises a mounting plate coupled to the outer duct, themounting plate being removably coupled to the heater to permit removalof the source of thermal energy.
 10. The heater of claim 9, wherein theheat exchanger is coupled to the heater via a twist-lock arrangement.11. A heater, comprising: an exterior case comprising an air inlet andan air outlet; a heater core within the exterior case and being incommunication with the air inlet and the air outlet; a fan communicatingwith the air inlet and the air outlet for moving air through the heatercore; said heater core comprising a source of thermal energy and a heatexchanger, the heat exchanger being disposed within the heater core andextending along a longitudinal axis extending between walls of saidexterior case wherein said air inlet and air outlet are disposed, theheat exchanger comprising an inner duct surrounding the source ofthermal energy and an outer duct surrounding the inner duct; and an airpathway defining a path of air movement progressing from the air inlet,through the heat exchanger, and out the air outlet, wherein the heatexchanger is removably coupled to the heater to permit removal of amodular unit comprising the outer duct and the source of thermal energy.12. The heater of claim 11, wherein the air pathway includes aserpentine pathway progressing through the heat exchanger.
 13. Theheater of claim 11, further comprising a dividing wall separating theheater core into a first portion adjacent the air inlet and a secondportion adjacent the air outlet, the dividing wall inhibiting fluidcommunication between the air inlet and air outlet, the dividing wallfurther comprising an opening extending therethrough and the heatexchanger being in fluid communication with the opening, such that airmoving through the heater core is forced to proceed through the heatexchanger.
 14. The heater of claim 11, further comprising an air jacketextending at least partially between the exterior case and the heatercore, the air jacket being adapted to provide a cooling airflow throughthe air jacket that does not pass through the heater core.
 15. Theheater of claim 11, said modular unit further comprising said innerduct.
 16. A heater, comprising: an exterior case comprising an air inletand an air outlet; a heater core within the exterior case and being incommunication with the air inlet and the air outlet; a dividing wallseparating the heater core into a first portion adjacent the air inletand a second portion adjacent the air outlet, the dividing wallinhibiting fluid communication between the air inlet and air outlet, thedividing wall further comprising an opening extending therethrough; afan communicating with the air inlet and the air outlet for moving airthrough the heater core; said heater core comprising a source of thermalenergy and a heat exchanger, the heat exchanger being disposed withinthe heater core and comprising an inner duct surrounding said source ofthermal energy and an outer duct surrounding the inner duct, wherein theheat exchanger is in fluid communication with the opening, such that airmoving through the heater core from the first portion to the secondportion is forced to proceed through the heat exchanger prior to beingdischarged through said opening and thereafter through the air outlet,wherein the heat exchanger is removably coupled to the heater to permitremoval of a modular unit comprising the outer duct and the source ofthermal energy.
 17. The heater of claim 16, wherein the inner duct iscoupled to the dividing wall about the opening.
 18. The heater of claim16, wherein the heat exchanger is disposed within the heater core andextends along a longitudinal axis extending between walls of saidexterior case wherein said air inlet and air outlet are disposed. 19.The heater of claim 16, further comprising an air jacket extending atleast partially between the exterior case and the heater core, the airjacket being adapted to provide a cooling airflow through the air jacketthat does not pass through the heater core.
 20. The heater of claim 16,wherein the heat exchanger further comprises a bracket adapted topositively couple the source of thermal energy to the heat exchanger,the bracket being at least partially removable from the heat exchangerto permit replacement of the source of thermal energy without removal ofthe heat exchanger from the heater.